In one example of electrographic methods, a latent electrostatic image is formed on an image bearing member by electrical charge and exposure, and subsequently developed by a toner-containing developer to form a toner image. Further, the toner image is transferred onto a recording material and then fixed. Meanwhile, the remaining toner on the image bearing member, which has not been transferred onto the recording material is cleaned by a cleaning member such as a blade disposed by welding with pressure on the surface of the image bearing member.
As a method for producing the toner, a pulverization method is known. The pulverization method is a method for producing the toner by melting and kneading one obtained by adding a colorant, and additives used if necessary to a thermoplastic resin as a binding resin, and subsequently pulverizing and classifying. However, the toner obtained in this way has large particle sizes, and it is difficult to form high-definition images using such toner.
Thus, the methods for producing the toner using a polymerization method or an emulsification dispersion method are known. As the polymerization method, a suspension polymerization method in which a monomer, a polymerization initiator, the colorant and a charge controlling agent are added in a water-based medium containing a dispersant with stirring to form oil droplets and then the polymerization is performed is known. An association method of agglutinating and fusion-bonding the particles obtained using the emulsification polymerization and the suspension polymerization is also known.
However, in these methods, although the particle diameter of the toner can be reduced, it is not possible to produce the toner containing a polyester resin or epoxy resin suitable for color toner as a major component of the binding resin because the major component in the binding resin is limited to a polymer obtained by radical polymerization.
Thus, the method for producing the toner using the emulsification dispersion method in which a mixture of the binding resin, colorant and the like is mixed with the water-based medium to emulsify is known (see Japanese Patent Application Laid-Open (JP-A) No. 05-666000 and JP-A No. 08-211655). This can reduce the particle diameter of the toner and additionally expands a range of choice for the binding resin. However, when such a method is used, fine particles are produced and emulsification loss occurs.
Thus, the method for producing the toner by emulsifying and dispersing the polyester resin and subsequently agglutinating and fusion-bonding the resulting particles is known (see JP-A No. 10-020552 and JP-A No. 11-007156). This can inhibit occurrence of the fine particles and reduce the emulsification loss.
However, the toner obtained by using the polymerization method or the emulsification method tends to become a spherical shape due to an interface tension of the liquid drops produced in a dispersion step. Thus, there is a problem that when a blade cleaning system is used, the spherical toner is hardly cleaned because the spherical toner rotates between a cleaning blade and a photoconductor to enter in spaces.
Thus, the method of making the particles amorphous by performing a stirring at high speed before termination of the polymerization to add a mechanical force to the particles is known (see JP-A No. 62-566560). However, when such a method is used, there is a problem that a dispersion state becomes unstable and the particles are easily integrated one another.
The method for obtaining association particles having the particle diameters of 5 to 25 μm by using polyvinyl alcohol having a particular saponification degree as the dispersant and agglutinating the particles is also known (see JP-A No. 02-51164). However, there is a problem that the association particle obtained in this way easily has the large particle diameter.
The method for making the particle amorphous by adding a filler together with a toner composition to an organic solvent is also known (see JP-A No. 02-51164). However, when the filler is added to the toner, a viscoelasticity of the toner is increased and a lower limit of the fixing is inhibited. When the filler is present on the toner surface, the viscoelasticity of the toner is scarcely increased, but when the substance such as filler is present in a toner surface layer, permeation of wax and melting out of the binding resin are inhibited as well as the fixing property at constant temperature and hot offset property are also inhibited.
Furthermore, a charge controlling agent obtained by exchanging ions such as metal ions present in an interlayer of a layered inorganic material with organic ions has been developed, and it has been proposed to use this for the toner for electrographs (see JP-A No. 2003-515795, JP-A No. 2006-50605, JP-A No. 2006-503313, JP-A No. 2003-202708, JP-A No. 2006-267911).
The toner for electrographs produced by a phase inversion method has been proposed (see JP-A No. 2006-267911). When the layered inorganic material exchanged with the organic ion is used for the toner electrographs produced by the phase inversion method, it is not sufficient as the charge controlling agent and the shape also becomes spherical. Although a reason is unknown, it is thought that the layered inorganic material exchanged with the organic ion is relatively evenly present in the vicinity of the aqueous phase before the phase inversion, but no uniform particle is made upon phase inversion, the layered inorganic material is unevenly present on the surface of toner particles and this is due to its unevenness.